Immunological milieu in mycosis fungoides and Sézary syndrome.

Tumor genesis and development are driven by a combination of intrinsic events such as oncogene activation and tumor-suppressor gene inactivation, and extrinsic events that are dependent on the interaction with the stroma. Different types of growth factors, cytokines and chemokines secreted by the surrounding stromal cells are thought to play key roles in solid tumor progression. Accumulating evidence indicates that the immunological milieu plays an essential role in tumor development, not only in solid tumors, but also in hematopoietic malignancies. Understanding the interactions between tumor cells and microenvironment in mycosis fungoides (MF) and Sézary syndrome (SS) could provide a basis for the development of new treatments for these diseases that are sometimes resistant to current therapies. This article focuses on the wide variety of cell types and immunological milieus, affecting the characteristic features of MF and SS, such as skin-homing of tumor cells, T-helper type 2-dominant tumor microenvironment, accumulation of dermal dendritic cells, epidermal hyperplasia, angiogenesis and pruritus.